Endotoxic shock was produced in unanesthetized sheep which had previously been depleted of T lymphocytes through a chronic thoracic duct fistula. This group of animals was compared to a non-depleted group which also received E. coli endotoxin. Both groups of animals had previously been instrumented for the recording of cardiopulmonary variables. Following the administration of endotoxin there were several differences in response between groups. The lymphocyte depleted group showed greatly reduced pulmonary hypertension and higher arterial PO2. They tended to have lowered total peripheral resistance and elevated myocardial contractility. It is apparent that the T lymphocyte plays an important part in the response to endotoxemia. A modified renal preparation was also developed. The preparation allows a complete battery of renal data to be collected, and also a limited amount of cardiopulmonary data. Following the administration of endotoxin, there was a complete renal shutdown. Experiments are in progress which involve treating the sheep with PGA1 after they have been subjected to endotoxic shock.